1. Field of the Invention
The present invention relates to a refrigerating apparatus.
2. Description of the Related Art
A refrigerating apparatus provided with a refrigerant circuit having a compressor, a condenser, an evaporator, and a heat exchanger in which nonazeotropic refrigerant mixture having a first refrigerant and second and third refrigerants with boiling points (evaporation temperatures) lower than a boiling point of the first refrigerant is sealed is known (e.g., see Japanese Patent Laid-Open No. 2003-13049).
The first refrigerant has, for example, a boiling point at which the refrigerant is liquefied when cooled by the condenser. The second and third refrigerants have boiling points lower than that of the first refrigerant and, for example, even if they are cooled by the condenser, not an entirety of them will be liquefied and a major part will remain in a gas state. The first refrigerant is a component required for compression by the compressor in the nonazeotropic refrigerant mixture and circulates through the refrigerant circuit while containing oil in the compressor.
In the refrigerant circuit, even if the second and third refrigerants are compressed by the compressor and cooled by the condenser, since a temperature of air or the like used for the cooling is high, not an entirety of them will be liquefied and an amount of the refrigerant gasified by the evaporator will be limited, and thus a cooling ability is not sufficiently utilized. Thus, a heat exchanger is provided which is configured to cool the refrigerant before being supplied to the evaporator with the refrigerant which has been brought to a low-temperature and low-pressure state by being gasified at the evaporator.
That is, in order to liquefy the second refrigerant and the third refrigerant having evaporation temperatures lower than that of the first refrigerant, cooling is performed by the heat exchanger.
By configuring in a manner described above, the second refrigerant and the third refrigerant of lower evaporation temperatures can be evaporated by the evaporator, and a temperature of the evaporator can be decreased.
In the above-mentioned refrigerating apparatus, although the first refrigerant compressed by the compressor is, after being cooled and condensed (liquefied) by the condenser and decompressed by a decompressor, evaporated (gasified) by the evaporator, since the evaporation temperatures of the second refrigerant and the third refrigerant at that time are lower than that of the first refrigerant, even if the second refrigerant and the third refrigerant are cooled by the heat exchanger in an air-cooling manner, the temperatures of the refrigerants are not sufficiently decreased, and a non-liquefied refrigerant (refrigerant in a gas state) remains. Therefore, problems may arise such as evaporation amounts of the second refrigerant and the third refrigerant of lower evaporation temperatures is not sufficiently obtained in the evaporator and the temperature of the evaporator is not decreased to a desired temperature.
On the other hand, a refrigerating apparatus is known in which, in order to cool an inner box to be housed in an outer box in an insulated manner, a refrigerant circuit having a compressor, a condenser, a decompressor, and an evaporator is provided and in which an evaporation pipe constituting the evaporator is attached in a meandering state to an outside of the inner box except at an opening (e.g., see Japanese Patent Laid-Open No. H03-158683).
In this refrigerating apparatus, the inner box is in a rectangular parallelepiped shape having a back plate, both side plates, a top plate, and a bottom plate and opened on the front, and the refrigerant circuit except for an evaporation pipe is housed in a machine chamber below the inner box. The evaporation pipe is first attached to the outside of the top plate in a meandering manner, then attached in a meandering manner in which a back-and-forth structure extending on the outside from one of the side plates via the back plate to the other side plate and extending on the outside from the other side plate via the back plate to the one side plate is repeated from an upper side to a lower side, and lastly, it is attached to the outside of the bottom plate in a meandering manner.
This refrigerating apparatus is configured in such a manner that, as the low-temperature refrigerant supplied from the machine chamber flows gradually from the upper side to the lower side along the outside of the inner box, uneven temperature distribution in an inside of the inner box (in the storage) due to a tendency that a cooled air remains at the lower side by its own weight can be made uniform.
The inner box of the refrigerating apparatus disclosed in the above-mentioned Japanese Patent Laid-Open No. H03-158683 forms a rectangular parallelepiped shape. For example, a boundary portion between the one side plate and the back plate forms a right angle, and a boundary portion between the other side plate and the back plate also forms a right angle.
When a tubular evaporation pipe made of metal is to be attached to the boundary portion forming a right angle, it is extremely difficult to bend the evaporation pipe at a right angle while bringing the pipe into thermal contact with the portion and maintaining a constant conductance.
Thus, when the evaporation pipe is to be attached to the refrigerating apparatus, it is, for example, necessary to individually attach the evaporation pipes respectively to the outside of the one side plate, the back plate, and the other side plate of the inner box in advance and to connect opening end portions of the evaporation pipes of the adjacent plates to each other by welding or to connect the opening end portions via a joint having a shape contouring the boundary portion by welding. However, since such a welding process is not easy, there is a problem that a manufacturing cost of the refrigerating apparatus is increased.
Alternatively, for example, as for the orthogonal boundary portion and a portion in its vicinity, it is necessary to bend the evaporation pipe so as to form an arc shape while a predetermined gap is maintained without bringing the evaporation pipe into thermal contact with the portions. However, there is a problem that such a portion which is not in thermal contact causes uneven temperature distribution inside the storage and the bending process is not easy. Thus, the problem of the increased manufacturing cost of the refrigerating apparatus still remains. Even if the refrigerating apparatus provided with the refrigerant circuit in which the above nonazeotropic refrigerant mixture is sealed is employed, since the evaporation amounts of the second refrigerant and the third refrigerant are not sufficiently obtained, it is difficult to prevent the uneven temperature distribution inside the storage.